1. Field of the Invention
The present invention relates to methods of manufacturing a nitride semiconductor device.
2. Description of the Background Art
Nitride semiconductor devices such as a nitride semiconductor light-emitting diode device, a nitride semiconductor laser device and a nitride semiconductor transistor device are manufactured using a substrate such as a gallium nitride substrate, a silicon carbide substrate or a sapphire substrate. Among these substrates, a sapphire substrate having advantages in cost, mass production and the like has been widely used.
Unfortunately, due to a high lattice mismatch ratio between a sapphire substrate and a nitride semiconductor layer such as gallium nitride formed on the substrate, many threading dislocations occur in the nitride semiconductor layer. The threading dislocations cause deterioration in various characteristics such as reduced luminous efficacy of a nitride semiconductor light-emitting diode device, reduced life of a nitride semiconductor laser device, and reduced electron mobility in a nitride semiconductor transistor device.
To address this issue, Patent Literature 1 (Japanese Patent Laying-Open No. 2002-43233), for example, discloses a method of reducing the dislocation density in a GaN layer arranged on a top surface by interposing a SiN layer between GaN layers.